An electromagnetic fuel injection valve used in an internal combustion engine, particularly in a cylinder fuel injection system, needs to supply an adequate fuel injection amount to an engine cylinder in order to comply with regulations of and satisfy demands for emissions and fuel economy. At this time, large variations in flow rate for each injection result in different combustion states among cylinders, which in turn lead to strong engine vibration and large engine sound, and further cause generation of unburned hydrocarbon and soot in the emissions. In recent years, market needs for the emissions control and the excellent fuel economy have been increased, and further improvement of the variations in flow rate has been demanded.
As a reason for the variations in flow rate, an influence of a change in a fuel path that is caused by variations in stroke length of a movable element can be raised. The stroke length of the movable element is determined by an axial distance between a fixed core and a fixed valve that are joined to a nozzle and by a total length of the movable element including a movable core. The fixed valve is joined to the nozzle by laser welding. If the fixed valve moves in an axial direction due to distortion at the time, a distance therefrom to the fixed core is changed, and the stroke length is also changed. A larger change in stroke further increases the variations in stroke length.
In order to handle the above, a structure has conventionally been known in which a space is provided in a welded section to alleviate stress concentration in a penetrated section by welding, so as to reduce the distortion by welding (for example, see PTL 1).